Protocol duplexer and protocol duplexing method

ABSTRACT

A method of duplicating protocol for making identical the order of reception and contents of packets on the two computers of a duplicated computer system with respect to packets of specific types of communication. On the first computer, each packet taken in is checked to determine whether the packet is a packet of the specific types of communication before protocol processing. If the packet is a packet of the specific types of communication, the packet is passed to the protocol processing process and added to a virtual queue created in its shared memory. On the second computer, each packet taken in is checked to determine whether the packet is a packet of the specific types of communication before protocol processing. If the packet is a packet of the specific types of communication, the packet is discarded, and the one at the head of the virtual queue in its shared memory is passed to the protocol processing process.

FIELD OF THE INVENTION

The present invention generally relates to a duplicated computer system, and in particular to the technology for duplicating protocol on a duplicated computer system.

BACKGROUND

There are various conventional methods of constructing a duplicated computer system using two computers each connected to a network. In such architectures, however, the order of reception of packets which are sent from the same sender and received by the two computers are not always the same. Although no problem occurs in uses for which the order of reception of packets does not matter if an switchover between the computers occurs in case of failure, it is not enough just to duplicate the hardware for uses in which the order of reception of packets matters.

The present invention was made to solve this problem. The object of the present invention is to provide a method of duplicating protocol so that the order of reception of packets and the contents of them on the two computers of a duplicated computer system are made identical for packets of specific types of communication, and a duplicated computer system with protocols duplicated in this manner.

SUMMARY OF THE INVENTION

The invention of claim 1 is a protocol duplicating configuration for making identical the order of reception and contents of packets on first and second computers which are connected to a network, have shared memories forming the same address space, and make up a duplicated computer system for packets of specific types of communication, characterized by having the following means on each of the first and second computers: queue holding means for storing packets to be processed in the order of reception; protocol processing means that is executed in response to reception of packets from the network; temporary queue holding means for temporally storing the packets having been processed by the protocol processing means; and virtual queue holding means for storing packets of the specific types of communication.

The invention of claim 2 is characterized in that the protocol processing means has packet taking-in means which takes in packets from the queue holding means and determines whether each packet taken in is a packet of the specific types of communication, protocol processing means for performing protocol processing on the packet, and packet output means for outputting the packet having been processed by the protocol processing means to the temporary queue holding means, and the protocol processing means on the first computer takes in the packets stored in the queue holding means by means of the packet taking-in means and determines whether each packet taken in is a packet of the specific types of communication, and if the packet is not a packet of the specific types of communication, performs the protocol processing on the packet by means of the protocol processing means and outputs the packet to the temporary queue holding means by means of the packet output means.

The invention of claim 3 is characterized in that the protocol processing means on the first computer takes in the packets stored in the queue holding means by means of the packet taking-in means and determines whether each packet taken in is a packet of the specific types of communication, and if the packet is a packet of specific types of communication, performs the protocol processing on the packet by means of the communication processing means and in addition stores the packet in the virtual queue holding means.

The invention of claim 4 is characterized in that the protocol processing means on the second computer takes in the packets stored in the queue holding means by means of the packet taking-in means and determines whether each packet taken in is a packet of the specific types of communication, and if the packet is a packet of specific types of communication, discards the packet and passes the packet at the head of the virtual queue to the communication processing means.

The invention of claim 5 is characterized in that the protocol processing means on the second computer takes in the packets stored in the queue holding means in order by means of the packet taking-in means and determines whether each packet taken in is a packet of the specific types of communication, and if the packet is a packet of the specific types of communication, compares the packet with the packet at the head of the virtual queue, and only if both packets are identical, discards the packet taken in and passes the packet at the head of the virtual queue to the communication processing means.

The invention of claim 6 is a method of duplicating protocol for making identical the order of reception and contents of packets on first and second computers which are connected to a network, have shared memories forming the same address space and make up a duplicated computer system for packets of specific types of communication, characterized by having the following steps executed on each computer: storing packets to be processed in a queue in order of reception; executing protocol processing in response to reception of packets from the network; temporally storing packets having been subjected to the protocol processing in a temporary queue; and virtual queue holding means for storing packets of the specific types of communication.

The invention of claim 7 is characterized in that the protocol processing step comprises: packet taking-in step which takes in packets from the queue and checks each packet taken in to determine whether the packet is a packet of the specific types of communication; protocol processing step which performs the protocol processing on the packet from the packet taking-in step; and packet output step which outputs the packet having been subjected to the protocol processing step to the temporary queue; and takes in the packets stored in the queue and checks each packet taken in to determine whether the packet is a packet of the specific types of communication by the packet taking-in step on the first computer, and if the packet is not a packet of the specific types of communication, performs the protocol processing on the packet by the communication processing step and outputting the packet to the temporary queue by the packet output step.

The invention of claim 8 is characterized by taking in the packets stored in the queue and checking each packet taken in to determine whether the packet is a packet of the specific types of communication by the packet taking-in step on the first computer, and if the packet is a packet of the specific types of communication, performing the protocol processing on the packet by the communication processing step and in addition storing the packet in the virtual queue.

The invention of claim 9 is characterized by taking in the packets stored in the queue in order and checks each packet taken in to determine whether the packet is a packet of the specific types of communication by the packet taking-in step on the second computer,and if the packet is a packet of the specific types of communication, discarding the packet and passing the packet at the head of the virtual queue to the communication processing step.

The invention of claim 10 is characterized by taking in the packets stored in the queue and checking each packet taken in to determine whether the packet is a packet of the specific types of communication by the packet taking-in step on the second computer, and if the packet is a packet of the specific types of communication, comparing the packet with the packet at the head of the virtual queue, and only if both packets are identical, discarding the packet and passing the packet at the head of the virtual queue to the communication processing means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram that shows only the part necessary for explanation of a duplicated computer system to which the method of duplicating protocol according to the present invention can be applied.

FIG. 2 is a diagram illustrating the principle of the method of duplicating protocol according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a simplified block diagram that shows only the part necessary for explanation of a duplicated computer system to which the method of duplicating protocol according to the present invention can be applied. In FIG. 1, a duplicated computer system 1 consist of two computers 10 and 20 that are connected to a network.

The computers 10 and 20 may have the same or different configurations depending on use. Since the necessary components are common to both computers 10 and 20, only those components are described below. Each of the computers 10 and 20 may be any type of computer as long as it has a processing circuit 11, 21 including a microprocessor and a memory not shown in the Figure, NIC (Network Interface Card) 12, 22 serving as the interface to the network, shared memory 13, 23 used for communication between the computers 10 and 20.

The NICs 12 and 24 are assigned the same MAC (Media Access Control) address Amac so that the computers 10 and 20 appear as a single computer to the network. The shared memories 13 and 23 are dual-port RAMs (Random Access Memories) used for making it possible for the computers 10 and 20 to have the same queue of packets of specific types of communication whose order of reception and contents must be identical on the first and second computers, and have the same addresses assigned to form the same address spaces (referred to as shared memory spaces) on the individual computers. The shared memories 13 and 23 are configured so that, when either computer 10 or 20 writes data to its own shared memory space, the same data is written to both shared memories 13 and 23 substantially at the same time.

Next, the operation of the duplicated computer system 1 is described below. The duplication of protocol according to the present invention is to forcibly make the order of reception and contents of packets on one computer identical to those of packets on the other computer with respect to packets sent from specified communication partners. For convenience sake, the case wherein the order of packets subjected to protocol processing on the computer 20 is made identical to that on the computer 10 is described below. The computer 10 is therefore referred to as the primary computer, and the computer 20 as the secondary computer.

FIG. 2 is a diagram illustrating the principle of the method of duplicating protocol according to the present invention. In FIG. 2, boxes 100 and 200 show protocol processing performed on the computers 10 and 20 in response to reception of packets from the network, for example. The protocol may be any one suitable for the use of the computer system 1, for example TCP (Transfer Control Protocol), but is a standard protocol with part of it modified as described later in detail. Assigned reference numbers 30 and 40 are queues in which packets to be processed by the protocol processing 100 and 200 are held in order. Assigned reference numbers 32 and 42 are queues in which packets having been processed by the protocol processing 100 and 200 are temporarily held. Since the same data are written to the shared memories 13 and 23 as described above, only one of them is shown in FIG. 2. In each of the shared memories 13 and 23, another queue 50 (referred to as a virtual queue) for holding only the packets from specified communication partners is created.

In actual operation, a packet is taken in from the queue 30 and checked to determine whether the packet is a packet (relevant packet) used in specific types of communication (relevant communication) for which the duplication of protocol according to the present invention is made, by queue taking-in processing 110 of the protocol processing 100 on the primary server 10. In the case where the duplicated computer system 1 receives packets from a network and the protocol is TCP, for example, whether the packet taken in is a relevant packet can be determined using the source MAC address, source IP address, and source port address in the packet, for example.

Further, the information (filtering information) used for determining whether the packet taken in is a relevant packet must not be limited to the above-mentioned source MAC address, source IP address, and source port address, but may be any information contained in packets as long as it can be used to identify packets. Moreover, since the types of communication for which the order of reception and contents of packets on the two computer must be made identical are expected to be limited depending on the use of the system 1, it may be preferable that the information used for identifying relevant types of communication or packets is stored in the nonvolatile memory of each computer beforehand by the manufacture, vendor or system administrator of the duplicated computer system 1.

In the queue taking-in process 110 on the computer 10, whether the packet taken in is a relevant packet is determined using the filtering information as described above. If the packet is not a relevant packet, it is simply passed to protocol processing 130. If the packet is a relevant packet, it is passed to the protocol processing 130, and also added to the virtual queue 50 in the shared memory 13. By this operation, only relevant packets are held in the virtual queue 50.

On the other hand, in the queue taking-in process 210 on the computer 20, the packet taken in is checked to determine whether the packet is a relevant packet in the same manner as in the queue taking-in process 110. If the packet taken in is not a relevant packet, it is simply passed to the protocol processing 250. If the packet is a relevant packet, either of the following two methods may be used: (1) Discarding the packet taken in and passing the packet at the head of the virtual queue 50 to the communication processing 250, and (2) Comparing the packet taken in with the one at the head of the virtual queue 50 (230) and, only if they are identical, discarding the packet taken in and passing the one at the head of the virtual queue 50 to the protocol processing 250.

By the processing described above, the same packets pass through the queues 32 and 42 in the same order with respect to relevant packets.

The present invention therefore can provide a method of duplicating protocol so that the order of reception of packets and the contents of them on the two computers of a duplicated computer system are made identical for packets of specific types of communication, and a duplicated computer system with protocols duplicated in this manner. 

1.-10. (canceled)
 11. A protocol duplicating configuration for making identical an order of reception and contents of packets on first and second computers which are connected to a network, have shared memories forming a same address space, and make up a duplicated computer system for packets of specified communications, characterized by having on each of the first and second computers: queue storing means for storing packets to be processed in order of being processed; protocol processing means that is executed in response to reception of packets from the network; temporary queue holding means for temporarily storing the packets having been processed by the protocol processing means in a queue; and virtual queue storing means for storing packets of target communication for the protocol duplication in a queue.
 12. The protocol duplicating configuration of claim 11, wherein the protocol processing means has packet taking-in means which takes in packets one by one from the queue storing means and determines whether each packet taken in is a packet of target communication for the protocol duplication, communication processing means for performing protocol processing on the packet, and packet output means for outputting the packet having been processed by the protocol processing means to the temporary queue storing means, and the protocol processing means on the first computer takes in the packets stored in the queue storing means one by one by means of the packet taking-in means and determines whether each packet taken in is a packet of the specified communication, and if the packet is not a packet of the specified communication, performs the protocol processing on the packet by means of the communication processing means and outputs the packet to the temporary queue storing means by means of the packet output means.
 13. The protocol duplicating configuration of claim 11, wherein the protocol processing means on the first computer takes in the packets stored in the queue storing means one by one by means of the packet taking-in means and determines whether each packet taken in is a packet of target communication for the protocol duplication, and if the packet is a target packet, performs the protocol processing on the packet by means of the communication processing means and in addition stores the packet in the virtual queue storing means.
 14. The protocol duplicating configuration of claim 12, wherein the protocol processing means on the first computer takes in the packets stored in the queue storing means one by one by means of the packet taking-in means and determines whether each packet taken in is a packet of target communication for the protocol duplication, and if the packet is a target packet, performs the protocol processing on the packet by means of the communication processing means and in addition stores the packet in the virtual queue storing means.
 15. A method of duplicating protocol for making identical the order of reception and contents of packets on first and second computers which are connected to a network, have shared memories forming the same address space and make up a duplicated computer system for packets of specified communication, characterized by comprising steps executed on each computer: storing packets received from said network in a queue in order of being processed; executing protocol processing in response to the reception of packets from the network; temporally storing packets having been subjected to the protocol processing in a temporary queue; and storing packets of target communication for the protocol duplication in a virtual queue.
 16. The method of duplicating protocol of claim 15, wherein the protocol processing step comprises: packet taking-in step which takes in packets one by one from the queue stored by the step of storing received packets in a queue and checks each packet taken in to determine whether the packet is a target packet for duplication; communication processing step which performs the protocol processing on the packet; and packet outputting step which outputs the packet from the communication processing step to the step of temporarily storing processed packets in a queue; and takes in the packets one by one from the queue stored by the step of storing received packets in a queue and checks each packet taken in to determine whether the packet is a target packet for duplication by the packet taking-in step on the first computer, and if the packet is not a target packet, performs the protocol processing on the packet by the communication processing step and outputs the packet to said step of temporarily storing processed packets in a queue by said packet outputting step.
 17. The method of duplicating protocol of claim 15, characterized by, on the second computer, taking in packets one by one from the queue stored by the step of storing received packets in a queue and checking each packet to determine whether the packet is a target packet for duplication by the packet taking-in step on the second computer, and if the packet is a target packet, comparing the packet with the packet at the head of the virtual queue, and only if both packets are identical, discarding the packet taken in and passing the packet at the head of the virtual queue to the communication processing means. 